Populating a taxonomy field through a Drupal migration.

Today's story is about how to populate a taxonomy term field in a node via a migration.

I’ll be using an XML file as my data source, and I’m using migrate, migrate plus and migrate tools modules to make life easier.

Prerequisite

• Create a taxonomy vocabulary named Published Date

• Add a new entity reference field with reference type set to the new vocabulary having machine name published_date in my custom XML node type
• Make sure to select Create reference entities if they don’t exist

A simplified migration file is shown below.

id: xml_migrate
label: 'XML Migrate - Level 1'
migration_group: xml_migrate_level_1
migration_tags:
  - xml_migrate_tag_1
source:
  plugin: url   # From migrate_plus module
  data_fetcher_plugin: file   # From migrate_plus module
  data_parser_plugin: simple_xml  # From migrate_plus module
  urls:
    - modules/custom/xml_migrate/sources/my-xml-data-source.xml
  item_selector: /node()[self::subordleg or self::act]
  fields:
    - name: leg_title
      label: 'Leg Title'
      selector: '@title
    - name: publication_date
      label: 'Publication Date'
      selector: '@publication.date'
  ids:
    leg_id:
      type: string
    publication_date:
      type: string
process:
  title:
    plugin: default_value
    source: leg_title
    default_value: 'New Node'
  field_leg_published_date:
    - plugin: entity_generate  # You can use different YML syntaxes
      source: publication_date
      entity_type: taxonomy_term
      bundle_key: vid
      bundle: published_date
      value_key: name
destination:
  plugin: 'entity:node'
  default_bundle: xml # Node Type
migration_dependencies: null

entity_generate Plugin break down

• plugin

We are using migrate plus process plugin entity_generate to create new terms to the Publication Date vocabulary if terms do not exist.

• Source

The field that was created named publication_date which will be populated by the data parser plugin using the given selector ‘@publication.date’

• entity_type

The entity type for taxonomy is taxonomy_term

• bundle

The machine name of the created taxonomy vocabulary. In this case it is published_date

• value_key

Value to compare in the bundle. This is a column name in the taxonomy_term_field_data table where the term values are stored. Usually it will be in name column

• bundle_key

Bundle key value. This is a column name in the taxonomy_term_field_data table where the term keys are stored. Usually it will be in vid column

And that's all to it !

I have not tried how it will work if you have the cardinality of the field_leg_published_date more than 1. So let me know if anything needs to be changed in the migration to allow that.

Resources

https://www.drupal.org/docs/8/api/migrate-api/migrate-process-plugins/contrib-process-plugin-entity_generate

https://www.drupal.org/docs/8/api/migrate-api/migrate-destination-plugins-examples/migrating-taxonomy-terms